The present invention generally concerns tool holding devices and the like, particularly those incorporating a centrally disposed bore for receiving a mating spigot of the tool part.
One device of this type is disclosed by Swiss Patent No. 537,770. Using this device, boring heads can be connected to an intermediate piece or shaft with high exchange accuracy and great stiffness. However, very high torques, such as occur when using particularly powerful machines, and such as are necessary for milling, boring and counter-boring tools, cannot be transmitted using this device.
The transmission of higher torques can be accomplished, in known fashion, using a variety of alternative means. For example, one alternative means which can be used is to double the transverse bore and retaining screw. This, however, apart from being awkward to deal with, also has the further disadvantage that exchange or repetition errors occur so that accurate positioning of the tool is not guaranteed. Another alternative which is available is the use of drive cams, however, this demands very high manufacturing accuracy and makes cleaning of the tool more difficult because of the existence of points which are difficult to access. Screw plug connections can also be used, but are not satisfactory because they can only rotate in one direction and are difficult to dismantle, and because they give an indeterminate position of the cutting edge. Axial clamping screws can be used, but have the disadvantage that the internal supply of coolant is only possible to a limited extent, and dealing with such devices is complicated.